kernel/kexec-Disable-at-runtime-if-the-kernel-enforces-modu.patch

From 1fc498d024c07e39105c060603e40cb7bc6bd5b8 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Fri, 9 Aug 2013 03:33:56 -0400
Subject: [PATCH 08/20] kexec: Disable at runtime if the kernel enforces module
 loading restrictions

kexec permits the loading and execution of arbitrary code in ring 0, which
is something that module signing enforcement is meant to prevent. It makes
sense to disable kexec in this situation.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 kernel/kexec.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index a785c1015e25..81d6b404f33c 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -36,6 +36,7 @@
 #include <linux/syscore_ops.h>
 #include <linux/compiler.h>
 #include <linux/hugetlb.h>
+#include <linux/module.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -1258,6 +1259,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 		return -EPERM;
 
 	/*
+	 * kexec can be used to circumvent module loading restrictions, so
+	 * prevent loading in that case
+	 */
+	if (secure_modules())
+		return -EPERM;
+
+	/*
 	 * Verify we have a legal set of flags
 	 * This leaves us room for future extensions.
 	 */
-- 
2.4.3